Revert "All functions now use shared_ptr<priv_queue>."

This reverts commit 0daa0b7aca4a57a517189928483d008ed07ba3f3.
Clearing collected processors from caches.
Start to separate queue_cache into header/impl.
Missing queue_cache impl from previous commit.
Suppliers own their priv_queues.

This means they are responsible for destroying and marking them.
Removing unnecessary (now) GC hack.